Internet Engineering Course

1. Internet Engineering Course Web Application Architectures

2. Agenda • Application servers • J2EE • .Net • Comparison between J2EE and .Net

3. mainframe terminals terminals 1. Application Servers • In the beginning, there was darkness and cold. Then, … Centralized, non-distributed

4. Application Servers • In the 90’s, systems should be client-server

5. Application Servers • Today, enterprise applications use the multi-tier model

6. Three-TierArchitecture

7. Web Application Architecture

8. Application Servers • “Multi-tier applications” have several independent components • An application serverprovides the infrastructure and services to run such applications

9. Application Servers • Application server products can be separated into 3 categories: • J2EE-based solutions • Non-J2EE solutions (PHP, ColdFusion, Perl, etc.) • And the Microsoft solution (ASP/COM and now .NET with ASP.NET, VB.NET, C#, etc.)

10. J2EE Application Servers • Major J2EE products: • BEA WebLogic • IBM WebSphere • Sun iPlanet Application Server • Oracle 9iAS • HP/Bluestone Total-e-Server • Borland AppServer • Jboss (free open source)

11. Web Server and Application Server App Server 1 Internet Browser Web Server(HTTP Server) HTTP(S) App Server 2

12. What is J2EE? • It is a public specification that embodies several technologies • Current version is 1.4 • J2EE defines a model for developing multi-tier, web based, enterprise applications with distributed components

13. J2EEArchitecture

14. J2EE Benefits • High availability • Scalability • Integration with existing systems • Freedom to choose vendors of application servers, tools, components • Multi-platform

15. J2EE Benefits • Flexibility of scenarios and support to several types of clients • Programming productivity: • Services allow developer to focus on business • Component development facilitates maintenance and reuse • Enables deploy-time behaviors • Supports division of labor

16. Main technologies • JavaServer Pages (JSP) • Servlet • Enterprise JavaBeans (EJB) • JSPs, servlets and EJBs are application components

17. JSP • Used for web pages with dynamic content • Processes HTTP requests (non-blocking call-and-return) • Accepts HTML tags, special JSP tags, and scriptlets of Java code • Separates static content from presentation logic • Can be created by web designer using HTML tools

18. Servlet • Used for web pages with dynamic content • Processes HTTP requests (non-blocking call-and-return) • Written in Java; uses print statements to render HTML • Loaded into memory once and then called many times • Provides APIs for session management

19. A Sample Scenario Other Components Web Server JSP (1) get a.jsp (2) process Client (5) HTTP file Servlet Impl. (3) gen. Servlet Database (4) result Servlet JVM

20. EJB • EJBs are distributed components used to implement business logic (no UI) • Developer concentrates on business logic • Availability, scalability, security, interoperability and integrability handled by the J2EE server • Client of EJBs can be JSPs, servlets, other EJBs and external aplications • Clients see interfaces

21. J2EE Multi-tier Model

22. J2EE Application Scenarios • Multi-tier typical application

23. J2EE Application Scenarios • Stand-alone client

24. J2EE Application Scenarios • Web-centric application

25. J2EE Application Scenarios • Business-to-business

26. J2EE Services and APIs • Java Message Service (JMS) • Implicit invocation • Communication is loosely coupled, reliable and asynchronous • Supports 2 models: • point-to-point • publish/subscribe

27. JMS • Point-to-point • Destination is “queue”

28. JMS • Publish-subscribe • Destination is “topic”

29. J2EE Services and APIs • JNDI - Naming and directory services • Applications use JNDI to locate objects, such as environment entries, EJBs, datasources, message queues • JNDI is implementation independent • Underlying implementation varies: LDAP, DNS, DBMS, etc.

30. J2EE Services and APIs • Transaction service: • Controls transactions automatically • You can demarcate transactions explicitly • Or you can specify relationships between methods that make up a single transaction

31. J2EE Services and APIs • Security • Java Authentication and Authorization Service (JAAS) is the standard for J2EE security • Authentication via userid/password or digital certificates • Role-based authorization limits access of users to resources (URLs, EJB methods) • Embedded security realm

32. J2EE Services and APIs • J2EE Connector Architecture • Integration to non-J2EE systems, such as mainframes and ERPs. • Standard API to access different EIS • Vendors implement EIS-specific resource adapters • Support to Corba clients

33. J2EE Services and APIs • JDBC • JavaMail • Java API for XML Parsing (JAXP) • Web services APIs

34. 3. EJB – a closer look

35. Home Interface • Methods to create, remove or locate EJB objects • The home interface implementation is the home object (generated) • The home object is a factory

36. Remote Interface • Business methods available to clients • The remote interface implementation is the EJB object (generated) • The EJB object acts as a proxy to the EJB instance

37. Remoting in Java • Several possibilities: RMI/CORBA • RMI can use JRMP or IIOP as a transport protocol • Not pluggable – changes in the code are necessary Client Server Stub/Skeleton-Layer Stub Skeleton Remote Reference Manager Transport Layer

38. EJB – The Big Picture

39. EJB at runtime Client can be local or remote

40. EJB at runtime

41. Types of EJB New!

42. Session Bean • Stateful session bean: • Retains conversational state (data) on behalf of an individual client • If state changed during this invocation, the same state will be available upon the following invocation • Example: shopping cart

43. Session Bean • Stateless session bean: • Contains no user-specific data • Business process that provides a generic service • Container can pool stateless beans • Example: shopping catalog

44. Entity Bean • Represents business data stored in a database  persistent object • Underlying data is normally one row of a table • A primary key uniquely identifies each bean instance • Allows shared access from multiple clients • Can live past the duration of client’s session • Example: shopping order

45. Entity Bean • Bean-managed persistence (BMP): bean developer writes JDBC code to access the database; allows better control for the developer • Container-managed persistence (CMP): container generates all JDBC code to access the database; developer has less code to write, but also less control

46. Message-Driven Bean • Message consumer for a JMS queue or topic • Benefits from EJB container services that are not available to standard JMS consumers • Has no home or remote interface • Example: order processing – stock info

47. Example of EJB Application • It consists of number of clients accessing session beans and entity beans • Each Session bean provides specialized processing on behalf of client e.g. Travel Agent session bean makes travel reservations while Flight Scheduler bean schedules planes to fly on various routes. • Each Entity Bean represent different type of business entity. e.g.Passengers, seats, planes, flights are entity beans

48. Example EJB Application

49. JBoss- J2EE Product FIND OUT MORE ABOUT TODAY’S MOST SUCCESSFUL OPEN SOURCE- DEVELOPED PPLICATION SERVER

50. What is Jboss? • Created in 1999, JBoss is the product of an OpenSource developer community dedicated to developing the best J2EE-compliant application server in the market • With 1000 developers worldwide and a steadily growing number of downloads per month, reaching 72,000 for October ’01 (per independent www.sourceforge.net), JBoss is arguably the most downloaded application server in the world today • Distributed under an LGPL license, JBoss is absolutely FREE for use. No cost. Period.